A deterioration states of a secondary battery includes a deterioration component produced by wear of the secondary battery (referred to as a wear deterioration component) and a deterioration component produced by a salt concentration imbalance in the secondary battery (referred to as a high-rate deterioration component). Patent Document 1 has described a technology in which the production of the high-rate deterioration component is detected on the basis of a difference between an electric current measured with a current sensor and an electric current estimated with a battery model.